FIGS. 1-2 represents an example of a conventional SAE J1772 (October 2012 Rev.) electric vehicle (EV) charging system 10 comprising an electric vehicle supply equipment (EVSE) 30, an EV connector 50, an EV charging receptacle 70, and an electric vehicle 90 (e.g., EVs, PHEVs, etc.). The EVSE 30 receives AC electric power at various nominal voltages and a frequency of 60 Hz (in the United States) from a utility grid or other power source and transfers it to the electric vehicle 90 battery 95 through a cord 35 and EV connector 50 that plugs into a mating EV charging receptacle 70 on the vehicle. The EVSE 30 can convert the grid AC power to DC output power, which is then provided to the electric vehicle 90, or alternatively, the EVSE could output AC power, to be converted to DC power internally by an EV on-board charger (not shown).
FIG. 2 shows an example of a conventional SAE J1772 EV connector 50. As is described in US 2011/0169447 A1, for example, the handle button 55 and the latch 51 are mechanically linked (e.g., by a spring-biased, pivoting lever) so that depression of the handle button 55 causes the latch 51 to move upwardly to permit insertion of (or removal of) the EV connector 50 into (or from) the corresponding EV charging receptacle 70. The latch 51 engages a corresponding, mating member in the EV charging receptacle 70 (e.g., a flange, detent, etc.) when the handle button 55 is released with the EV connector 50 inserted into the EV charging receptacle 70 and, in the engaged position, this positive engagement prevents inadvertent decoupling.
Five contacts C1-C5 are depicted at the head of the EV connector 50. The contacts C1-C5 includes conductive elements that mate with corresponding conductive elements (not shown) in the EV charging receptacle 70 to provide an electrical path therebetween. Contact C4, for example, enables basic two-way communications between the EVSE 30 and the vehicle 90 via a control pilot signal.
The function of the handle button 55 is to control the latch 51 holding the EV connector 50 in the EV charging receptacle 70. Contacts C3 and C5 at the EV connector 50 to EV charging receptacle 70 interface indicate to the EVSE 30 when the EV connector 50 is properly connected to an EV charging receptacle 70. Contact C3 is electrically connected to the EVSE 30 equipment ground and to the vehicle chassis ground. As set forth in SAE J1772, Section 4.2.2, opening of the handle button 55 should trigger the vehicle charge control to provide a controlled shutoff or charge power prior to disconnection. As set forth in SAE J1772, Section 6.2.2, the EVSE monitors its proximity circuit and charging is only allowed when the EVSE detects a valid proximity circuit voltage with no faults and with the handle button 55 switch closed.
FIG. 3 shows, in accord with the SAE J1772 standard, a conventional proximity detection circuit enabling verification of the mechanical connection between the EV 90 and the EVSE 30. The implementation details of proximity detection are, however, left to the discretion of the manufacturer. The handle button 55 is a part of this proximity detection circuit and is normally closed, except when the connector latch 51 is actuated to decouple the connector from the EV charging receptacle 70.
FIG. 4 shows a representation of a conventional AC Level 2 system configuration (Nominal Supply Voltage (V) of 208 to 240 VAC, less than or equal to 80 A continuous) including the circuit of FIG. 3, as disclosed in the SAE J1772 standard (October 2012 Rev.). AC power from an electric supply is provided to an on-board charger 91 using an appropriate EV connector 30 and cord set. The EVSE 30 provides required ground fault protection (GFI) 34 between the electric supply and the vehicle 90. If there is a non-symmetrical impedance connection between the onboard power electronics and the vehicle frame ground, it will be picked up by the GFI sense coil 34 in the EVSE 30. If the connection generates a current that is above a pre-determined threshold, the EVSE control electronics 32 will cause the contactor/relay 36 to break the electrical connection between lines L1, L2, connected to the power grid, and the vehicle 90.
The SAE J1772 standard specifies some minimal human-machine interface (HMI) between the EVSE 30 and the user, such as a required “power-on indication” or “AC Present” indicator (SAE J1772 4.6.5) that the EVSE is connected to AC main power and a “charge status indicator” (SAE J1772 4.2.2.3) providing charge status information visible to the operator while inserting the EV connector 50 into the EV charging receptacle 70. Additional HMI functions to extend the capabilities of the EVSE 30 may be provided at the discretion of the EVSE manufacturer and may include buttons, keypads, touch screens, or the like, to enable a user to set a charging time, set a charging delay, or to enable display functions such as the display of a charging current. For example, some commercially available EVSE HMIs allow the user to set a charging delay when connecting their electric vehicle 90 (e.g., EVs, PHEVs, etc.) to the EVSE 30 to allow the user to avoid peak demand billing rates.